In-situ tensile test scanning electron microscopy dataset for solutionized Inconel 718

High-resolution Digital Image Correlation (HR-DIC) was performed on an Inconel 718 specimen, which was subjected to a heat treatment to form a fully solutionized system. In-situ measurements in the small strain regime were made through SEM imaging, followed by HR-DIC to extract quantitative representations of the strain and in-plane displacement induced by deformation events during plastic deformation.

Methods
Material: The present study investigated a nickel-based superalloy, Inconel 718. The Inconel 718 material was subjected to an annealing treatment at 1050◦C for 30 minutes, followed by water quenching to produce a nearly random texture and a grain size distribution centered at 65 μm.

Mechanical Testing: Flat dogbone-shaped specimens were prepared for testing with a gauge section measuring 1×3 mm2. Tensile loading was conducted at room temperature under a quasi-static strain rate using a custom 5000 N in situ load stage. The loading was intermittently interrupted at four points through past yield to acquire backscatter SEM images. Load was not removed during the SEM imaging. Macroscopic engineering strain was measured in situ using fiducial markers positioned at both ends of the gauge length, while macroscopic engineering stress was determined by dividing load cell output by the sample cross section. The points where loading was interrupted for detailed SEM imaging correspond to total strain levels of 0.38%, 0.62%, 1.02%, and 1.95%.

High-Resolution Digital Image Correlation: High-resolution digital image correlation measurements were conducted using a ThermoFisher Versa3D scanning electron microscopy (SEM) and Scios field emission gun system. Surface preparation for both specimens involved mechanical polishing with SiC papers up to 1200 grit, followed by polishing with a 3 μm diamond suspension, and a final chemomechanical polish using 0.05 μm colloidal silica for 12 hours. The speckle pattern for HR-DIC was created using gold or silver nanoparticles. The resulting pattern had a high density of 60 nm nanoparticles suitable for HR-DIC measurements. High magnification images were captured at horizontal field widths (HFWs) of 137 μm. Each SEM image consists of a 0.137 mm × 0.137 mm region discretized into 4096 × 4096 points, yielding a spacing or pixel size of 33.4 nm. A series of 8 by 8 images were then collected to generate a composite image of approximately 1 mm × 1 mm in size of the sample gauge section.

Electron Backscatter Diffraction: Prior to deformation, electron backscatter diffraction (EBSD) measurements were performed. EBSD measurements were performed with an
EDAX OIM-Hikari detector, using a step size of 0.8 μm. Diffraction patterns were obtained with an accelerating voltage of 20 kV, a 4 × 4 binning, and a beam current of 0.2 nA.